U.S. patent number 4,410,443 [Application Number 06/380,980] was granted by the patent office on 1983-10-18 for method of dissolving iron oxide-chrome oxide spent shift catalysts to prepare a nitrate solution suitable for use in preparing a new catalyst.
This patent grant is currently assigned to Katalco Corporation. Invention is credited to George N. Pessimisis.
United States Patent |
4,410,443 |
Pessimisis |
October 18, 1983 |
Method of dissolving iron oxide-chrome oxide spent shift catalysts
to prepare a nitrate solution suitable for use in preparing a new
catalyst
Abstract
A method of preparing a solution of the nitrate of iron and
mixed chromium from a spent iron oxide-chrome oxide shift catalyst
which comprises dissolving said spend iron oxide-chrome oxide shift
catalyst with nitric acid in the presence of from 5-25% by weight
of the catalyst of an additive selected from the group consisting
of ferrous sulfate and sodium thiosulfate.
Inventors: |
Pessimisis; George N.
(Westchester, IL) |
Assignee: |
Katalco Corporation (Oak Brook,
IL)
|
Family
ID: |
23503197 |
Appl.
No.: |
06/380,980 |
Filed: |
May 24, 1982 |
Current U.S.
Class: |
252/182.33;
423/395; 423/53; 502/24 |
Current CPC
Class: |
C01G
49/009 (20130101); C01G 49/00 (20130101) |
Current International
Class: |
C01G
49/00 (20060101); C09K 003/00 () |
Field of
Search: |
;252/413,182
;423/395,150,53 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
19989 |
|
Dec 1980 |
|
EP |
|
1252176 |
|
Nov 1971 |
|
GB |
|
1259381 |
|
Dec 1971 |
|
GB |
|
Primary Examiner: Garvin; Patrick
Assistant Examiner: Piezlock; Cynthia A.
Attorney, Agent or Firm: Premo; John G. Miller; Robert
A.
Claims
Having thus described my invention, I claim:
1. A method of preparing a solution of the nitrate of iron and
mixed chromium from a spent iron oxide-chrome oxide shift catalyst
which comprises dissolving said spent iron oxide-chrome oxide shift
catalyst with nitric acid in the presense of from 5-25% by weight
of the catalyst of an additive selected from the group consisting
of ferrous sulfate and sodium thiosulfate.
Description
This invention relates to solution preparation, in particular of
the nitrates of iron and chromium.
The iron-chrome shift catalyst, when in use, contains a mixture of
divalent and trivalent iron oxides, in combination with trivalent
chromium oxide, and is usually brought into its active form by
reducing an oxide precursor composition in a higher valency state.
Some oxide compositions used in the past have contained hexavalent
chromium, but this is undesirable because of toxicity and of the
large heat evolution during reduction. It has, therefore, been
proposed to reduce the hexavalent chromium to trivalent chromium
during production of the oxide composition, for example by reaction
with a divalent iron compound such as ferrous carbonate. This has
the drawback that the only inexpensive iron compound from which the
ferrous carbonate could be made is ferrous sulphate, so that steps
have to be taken to avoid contamination of the oxide composition by
sulphur or to prolong the reduction treatment until sulphur
compounds have been driven out. Among the methods proposed for
making low-sulphur oxide compositions are that described in UK No.
1,259,381, which describes an initial stage of precipitation of
ferrous oxalate, and that described in UK No. 1,252,176, which
describes thermal decomposition of nitrates. These methods are
expensive, especially that of 1252176 because of the cost of the
chromium nitrate and, accordingly, European published application
No. 19989 which describes a method of making a solution of the
nitrates of iron and chromium by reacting metallic iron or an alloy
thereof with nitric acid in the presence of one or more hexavalent
chromium compounds. Thereafter, the nitrates are converted to an
intimate mixture of the oxides, preferably by way of
co-precipitating them with an alkaline reactant.
Since iron-chrome shift catalyst has to be replaced after a few
years' use, it would be very convenient if it could be converted to
the mixed nitrate solution and, thus, to fresh catalyst. This
invention is thus directed to the dissolution of spent
high-temperature shift catalyst containing iron and chromium oxides
with nitric acid.
THE INVENTION
I have discovered that when ground-high temperature spent iron and
chromium oxide containing shift catalyst is treated with nitric
acid and one or more additives from the group consisting of ferrous
sulfate and sodium thiosulfate, remarkable dissolution of the spent
catalyst is achieved.
HIGH TEMPERATURE SHIFT CATALYST
Compositions which are meant to be treated in this invention
include iron oxide-chrome oxide shift catalyst and other iron
oxide-chrome oxide catalyst compositions. The iron oxide-chrome
oxide ratios of these materials may vary considerably, and it will
be seen that the method described in this invention generally
applies to all spent catalyst materials containing principally iron
oxide and/or chrome oxide.
THE DISSOLUTION STEP
Dissolution of the iron-chrome catalyst is carried out in the
following steps:
A. The iron-chromium oxide catalyst is ground;
B. The ground iron-chromium oxide catalyst treated with nitric acid
and one or more additives of this invention;
C. The resultant slurry is then heated for a period of time, so as
to obtain substantial dissolution of the iron-chrome catalyst
material.
The nitric acid that may be utilized in this invention ranges in
concentration from as low as 10% to as high as 64% HNO.sub.3.
Technically, in the process of this invention, a solution is made
by first adding concentrated nitric acid to water, and then adding
the shift catalyst to this solution. After the shift catalyst is
added, the additives of the instant invention are employed.
The concentration of nitric acid employed will be seen and will be
apparent to those skilled in the art and those familiar with
handling acid materials.
The additives employed, as stated above, are ferrous sulfate and
sodium thiosulfate. Generally, these additives will be present at a
level of from 5-25% by weight of the spent catalyst that is to be
dissolved. In an especially preferred composition of this
invention, 15% ferrous sulfate, based upon the weight of the
catalyst, is employed; and 2% sodium thiosulfate is employed based
upon the weight of the catalyst to be dissolved, so as to give a
total of 17% additive based upon the weight of the catalyst.
It will be seen that one additive may be used without the other or
both additives may be used, as in the preferred practice of the
invention, with each other.
The quantity of nitric acid used is preferably sufficient to
dissolve the catalyst completely, in order to avoid changing the
ratio of iron to chromium. Incomplete dissolution of the catalyst
may, on occassion however, have to be accepted when, for instance,
a catalyst has suffered accidental overheating or has been used at
unusually high temperatures, such as in reducing gas production. In
any event, however, it is advisable to check and, if necessary,
adjust the iron to chromium ratio of the solution after dissolution
has taken place prior to using the solution to form a new catalyst
material.
Resultant nitrate solution of iron and chromium can then be
employed in the preparation of new shift catalyst.
EXAMPLES
To 450 milliliters of water was added 385 cc of 63% HNO.sub.3, 100
grams of dry ground spent shift catalyst analyzed as containing 90
weight percent Fe.sub.3 O.sub.4, 8 weight percent Cr.sub.2 O.sub.3,
15 grams of ferrous sulfate, and 2 grams of sodium thiosulfate.
This slurry was then heated to 212.degree. F. under refluxing
conditions for three hours. A greenish solution with some
percipitate was obtained. After cooling, slurry was filtered. Seven
hundred forty milligrams of greenish filtrate and 10.2 grams of
undissolved catalyst were obtained.
To show the effect of the additives of the instant invention, the
identical experiment was repeated as above with the exception being
that the ferrous sulfate and sodium thiosulfate were omitted. The
amount of undissolved catalyst obtained in this instance was 85
grams or 85% of the resultant starting material.
* * * * *